The phrase "bedrock principle" refers to a fundamental belief or value that serves as a strong foundation for other ideas or actions. It is an essential principle that everything else is built upon. Full definition
The third bedrock principle of Ben Graham value investing system is that a security is an ownership interest in an actual business rather than a piece of paper to be traded based on person's view about the views of other people, about the views of other people [repeat]. (25iq.com)
The third bedrock principle of value investing is: Margin of safety! (25iq.com)
The second bedrock principle of Ben Graham - style value investing is that a security must be purchased at a sufficient bargain to intrinsic value that it provides the investor with a margin of safety. (25iq.com)